1. Field of the Invention
The present invention relates generally to a piston-cylinder unit such as for a shock absorbing strut, or vibration damping strut, of a motor vehicle. The piston-cylinder unit can include a cylinder in which a piston rod can be located. The piston rod can move axially with respect to the cylinder. The piston rod can be connected to a first connection mechanism, and the cylinder can be connected to a second connection mechanism. A positioning cylinder can be connected to one of the first and second connection mechanisms. The distance between the first and second connection mechanisms can be set by the addition or discharge of pressure medium via a pressure medium connection to the positioning cylinder.
2. Background Information
A known piston-cylinder unit is described in German Laid Open Patent Application No. 42 31 641 (corresponding to U.S. Pat. No. 5,401,053). In this type of piston-cylinder unit, the distance between the connection mechanisms is controlled by the feed and discharge of pressure medium to maintain a defined level position. One disadvantage of the piston-cylinder unit constructed according to the teaching of German Laid Open Patent Application No. 42 31 641 is that the cylinder, by means of its inside diameter, forms a running path or track for the piston of the piston rod. Furthermore, the outside diameter represents a running path for the positioning cylinder.
If one were to take a cross section through the piston-cylinder unit in the vicinity of the piston, it would be apparent that the cylinder is a component of a double fit between the piston and the positioning cylinder. The inside diameter must be precisely fabricated as a running path for the piston, and a corresponding precision is required for the outside diameter. For example, the inside diameter can be calibrated or finished to size by a refinishing of the inside or outside diameter. Consequently, under some conditions, it may not be possible to refinish the outside diameter to the desired size, because it would thereby change the inside diameter.